The existence and characteristics of simple nitronium salts such as nitronium hexafluoroarsenate, nitronium hexafluorophosphate and nitronium tetrafluoroborate have been known for some time. For example, nitronium hexafluoroarsenate is a colorless, crystalline solid that is stable at room temperature and sensitive to moisture. The salt is soluble in nitromethane and, like other nitronium salts, is an excellent nitrating agent for aromatics and a good oxidizing and intercalating agent for covalent materials such as graphite and polyacetylene.
The recent interest in nitronimum hexafluoroarsenate, (NO.sub.2 AsF.sub.6) as an oxidizing agent has emphasized the need for a simple, one-step, high yield synthesis of this compound. Previous syntheses have involved the initial preparation of nitryl fluoride (FNO.sub.2) (from NO.sub.2 and F.sub.2) and subsequent reaction with arsenic pentafluoride (AsF.sub.5); the use of hydrogen fluoride (HF) with nitric acid (HNO.sub.3), nitryl chloride (ClNO.sub.2) or nitrate esters; the reaction of nitrogen dioxide (NO.sub.2), bromine trifluoride (BrF.sub.3), and arsenic pentoxide (As.sub.2 O.sub.5); the use of fluorine nitrate (FNO.sub.3); or metathesis reactions from other AsF.sub.6.sup.- salts. These reactions generally were run in metal cylinders or quartz vessels and were multi-step.
In all cases, the process is made more expensive and chemically complicated by the fact that the reagents are incompatable with Pyrex.TM. glass. NO.sub.2 F and HF cannot be made to contact Pyrex.TM. glass because silicon tetrafluoride (SiF.sub.4), which would contaminate the product, is also generated. The reagents in this new process, are compatible with dry Pyrex.TM. glass under the reaction conditions, and no SiF.sub.4, or SiF.sub.6.sup.2- salts contaminate the product.